Dynamic Data Display - WPF - Need to add text to canvas - C#

Question

I am using the dynamic data display WPF chart. I have a requirement to display a label next to every point on the curves plotted on the chart.

The exact functionality is as follows:

Every curve has a an object that holds its data and a description that inculdes color, marker shape etc. It also tell me whether the labels must be visible for that particular curve.
There is also an option using a checkbox to hide/show the labels for all points on all the curves on the plot.
There is a third option where a user can left click on the marker and see a label next to it.

Now, I previously implemented it by adding labels along with the ElementMarkerPointGraph for each point and setting the visibility of the labels. I know there is a massive performance hit with this approach.

I am now looking to create a solution where I can render text directly to the canvas at a location that I provide. I also need help with the removing the text from the canvas.

Is there a way of adding text natively to the canvas? What is the most efficient way to do so?

EDIT: I need to move the text around as the plotter zooms. I already know when the plotter zooms, I need to be able to move the text to the appropriate location.

Hard to tell with no code. How do you display the curves? Could we have the piece of XAML that actually drw the curves ? — Kek, Nov 14 '12 at 07:30
It uses the extension methods in Plotter2DExtensions class. You can have a look at the D3 source code on codeplex. Anyway, I have decided to use the OnRender method to achieve this. Thanks! [link]http://dynamicdatadisplay.codeplex.com — Harsha, Nov 14 '12 at 08:46

score 22 · Answer 1 · edited Nov 14 '12 at 16:14

22

I'm not sure whether this will give you the zooming purpose but the code below can be used to add text inside a canvas..I got it from a site while googling.

private void Text(double x, double y, string text, Color color) 
{
    TextBlock textBlock = new TextBlock();
    textBlock.Text = text;
    textBlock.Foreground = new SolidColorBrush(color);
    Canvas.SetLeft(textBlock, x);
    Canvas.SetTop(textBlock, y);
    canvasObj.Children.Add(textBlock);
}

edited Nov 14 '12 at 16:14

Jason Higgins

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answered Nov 14 '12 at 07:26

hridya pv

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Thanks! But I already knew to add textblock but I was looking to avoid using more controls. :) – Harsha Nov 14 '12 at 08:44

score 6 · Answer 2 · answered Nov 27 '12 at 06:17

OK. My exact implementation can't be put up here. But I can provide some idea of how to do it.

So create a simple user control that derives from Canvas.

class CustomCanvas : Canvas
{
    protected override void OnRender(DrawingContext dc)
    {
        FormattedText someFormattedText = new FormattedText(someText, System.Globalization.CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
                someTypeFace, someFontSize, someColor);
        dc.DrawText(someFormattedText, new Point(15, 15));
    }
}

You can seal the class, if you do not want it subclassed/overriden further.

That's about it. You can check out the other methods available with the drawing context to do some other stuff. :)

score 2 · Answer 3 · answered Nov 14 '12 at 08:43

2

I figured it out myself. I'll be overriding the OnRender method to handle this. I can draw text using the drawing context.

answered Nov 14 '12 at 08:43

Harsha

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Dynamic Data Display - WPF - Need to add text to canvas - C#

3 Answers3